The head of the Federal Aviation Administration faced another grilling in Congress on Wednesday following revelations that pilots complained to Boeing about the 737 MAX in the aftermath of the Lion Air crash.

The hearing comes amid a near-constant trickle of news reports in recent weeks that have raised pointed questions about both Boeing's and the FAA's handling of an aircraft that has been grounded globally following two deadly crashes that left 346 dead.

News reports on the eve of the hearing chronicled a November 27 meeting after the Lion Air crash at which American Airlines pilots pressed Boeing for safety changes that could have temporarily grounded the plane.

Another report on Tuesday said the FAA did not independently evaluate the safety of a Boeing 737 MAX system implicated in the two deadly crashes, deferring to Boeing on key judgments.

In three-hour testimony, Acting FAA Administrator Daniel Elwell broadly defended the agency's handling of the 737 MAX certification. Critics have accused the FAA of being too cozy with Boeing, inhibiting its ability to effectively regulate the company.

Elwell said the fact that there had been only one airline fatality in the United States over the last decade was evidence of a safety record 'that is in many ways remarkable,' while adding 'we know that our oversight approach needs to evolve.'

But the FAA chief, who hedged his criticism of Boeing over the disasters, faced plenty of tough questioning, including about the agency's move to ground the 737 MAX only after virtually every other civil aviation authority had already taken the plane out of service.

Elwell said the US body acted only after 'data' showed a connected between the October Lion Air crash and the March Ethiopian Airlines crashes.

'So the opposite of data is common sense,' said Representative Steve Cohen, a Tennessee Democrat.

'It just seems like common sense should have taken control,' he said 'Data is fine but it's something that's right before your eyes.'

Key info 'languished'

Lawmakers also pressed the FAA about revelations that Boeing knew that a sensor linked to a flight handling system did not work properly for more than a year before it notified the agency.

In both crashes, the system, called the Maneuvering Characteristics Augmentation System, pointed the plane sharply downward based on a faulty sensor reading, hindering pilot control after takeoff, according to preliminary crash investigations.

The information 'languished' at Boeing, Elwell acknowledged.

'I am not happy about a 13-month gap,' he said, adding that the agency would fix the issue.

Reports Tuesday in The New York Times and The Dallas Morning News recounted the November meeting at which pilots pressed Boeing to take more aggressive action to ensure the safety of the MCAS, complaining that information about the system was not included in training manuals.

Elwell said he first learned about a late-November American Airlines pilots meeting with pilot from news reports.

Elwell appeared to hedge when asked whether Boeing should have notified the FAA of the pilot concerns, saying 'anytime a manufacture becomes aware of a critical safety issue, it should be made known to the FAA.'

Most of the toughest questions came from Democrats, with some Republicans on the panel expressing support for the FAA and for Boeing.

Representative Sam Graves, Republican of Missouri, said the Lion Air and Ethiopian Airlines crashes illustrated problems with pilot training and with the capacity of overseas regulators.

The FAA is still the 'gold standard,' Graves said.

'What scares me is climbing on an aircraft or airline that is outside US jurisdiction. ... It just bothers me that we continue to tear down our system based on what has happened in two other countries.'

Need for international coordination

The FAA is overseeing Boeing's MCAS upgrade as both it and Boeing face federal investigations, including by the US Department of Justice.

Major US carriers have said they expect to resume flights on the 737 MAX in August but that timeframe is contingent on FAA approval of the upgrade.

The FAA has called a May 23 meeting of international civil aviation regulators to Texas to discuss the FAA's process for clearing the 737 MAX to resume service.

Elwell said his hope was for better coordination in returning the 737 MAX to the skies than had been the case in grounding it, when global aviation authorities acted separately.

'There's a perception of a crisis of confidence with the design of the plane and maybe wider,' Elwell said.

'It's important that we are collaborative and act transparently,' he said. After the May 23 meeting, 'my hope is that they have the confidence in our work to make their un-grounding as close to ours as possible.'